1. Field of the Invention
The present invention relates to an ink jet printer that performs recording by discharging ink from the ink jet recording head to a recording medium. More particularly, the invention relates to an ink jet printer provided with a cleaning unit whereby to clean the discharge port surface of the ink jet recording head.
2. Related Background Art
There is a screen printing method, as a typical one, that uses silk screen form plates to print directly on paper for the production of a large poster or a camp. In accordance with this method, each of the silk screen form plates is mounted, at first, on a screen printing apparatus per color corresponding to colors used for the original image to be printed, and then, ink is transferred directly to the paper sheet through meshes of the silk screen form plates for recording.
However, it takes a great number of processes and time to prepare the silk screen form plates in advance. In addition, ink adjustment should be made for each color, and also, each of the silk screen form plates should be positioned, among some other operations needed.
Further, the size of the apparatus is large, and it becomes larger in proportion to the number of colors to be used, which requires not only a larger space for installation of the apparatus, but also, it requires a space for storing the silk screen form plates.
Also, with a printing method of the kind, it is possible to perform a large scale production at extremely low costs, but the costs become extremely high if posters should be produced in a smaller lot for a presentation, for a single event, or the like.
Here, therefore, as one of the suitable methods for printing in a smaller lot, an ink jet recording method has been proposed, which enables images to be recorded directly on a recording medium. In accordance with this ink jet recording method, fine ink droplets are discharged from the discharge ports provided for ink jet recording means (an ink jet recording head), and fly onto a recording medium, such as a paper sheet, thus recording images on the recording medium. With this method, it becomes unnecessary to prepare the screen form plates needed for the screen printing as described above. As a result, it is possible to curtail a great number of processes and time needed before the formation of images on the paper sheet. It also becomes possible to make the apparatus much smaller. Also, image information needed for the execution of printing can be stored on a medium, such as a tape, a flexible disc, an optical disc, hence making it possible to provide an excellent storage and reservation of the image information. In addition, there is a great advantage that image processing can be executed easily to change color arrangements, to modify layout, to prepare the enlargement or reduction of sizes, and so on with respect to the original images.
Of the ink jet recording apparatuses, the serial type recording apparatus, which records on a recording medium while executing its main scan in the direction intersecting the conveying direction of the recording medium (that is, the sheet feeding direction or the sub-scanning direction), is capable of recording in a desired area on the recording medium by repeating its operating in such a manner that the sheet feed is executed for a specific amount (the pitch feed to perform the sub-scanning) after the completion of the recording of one-line portion which has been made by recording (main scanning) an image by use of the recording means that travels along the recording medium, and that the recording (main scanning) is made for the next line portion of the image on the recording medium that has come to a stop subsequent to the last pitch feed.
On the other hand, the line type recording apparatus, which is arranged to record on a recording medium only by means of the sub-scanning in the sheet feed direction, records an image in the desired area on the recording medium by setting the recording medium in a specific recording position, and then, the sheet feed (pitch feed) is performed altogether while continuously recording one line portion after another.
In general, the ink jet type recording apparatus (ink jet recording apparatus) is arranged to record on a recording medium by discharging ink from recording means (recording head) to the recording medium, and the recording means (recording head) can be made compact easily for recording images in higher precision at higher speeds. Also, with the ink jet recording apparatus, it is possible to record on an ordinary paper sheet without any particular treatment given to it, which contributes to making its running costs lower. Also, this recording method is of non-impact type, having a lesser amount of noises in operation, among some other advantages such as an easier recording of color images by use of various kinds of ink (color ink, for instance).
Particularly, the ink jet type recording means (recording head) that discharges ink by the utilization of thermal energy is produced by arranging the electro-thermal converting means, electrodes, liquid path walls, a ceiling plate, and the like on a substrate by the application of film formation techniques using the semiconductor process, such as etching, vapor deposition, sputtering, or the like. In this manner, this recording means can be fabricated more compactly and easily with the arrangement of highly densified liquid paths (the arrangement of discharge ports). Also, by the utilization of the IC technologies and techniques, as well as the advantages of the micromachining, it is easier to elongate the recording means or to plane it (make it two dimensional) for the easier provision of fully multiple recording means, and the highly densified assembling thereof as well.
Also, in recent years, there are various demands on the kinds of recording media using different materials. Along with the developments that have been made to meet such demands, it becomes possible for a recording apparatus to use cloth, leather, unwoven stuff, or even metal, in addition to the usual recording medium, such as paper sheet (including thin paper, processed paper sheet) or thin resin plate (OHP or the like).
However, since the ink jet recording apparatus discharges ink from extremely fine discharge port formed on the discharge port surface of the recording head, it is subjected to the adhesion of foreign substances to the discharge port surface, such as solidified ink, paper particles, ink droplets, or the like. (For example, the tail portion of a main droplet becomes a fine droplet due to the surface tension of ink itself when the ink droplet is discharged for the execution of ink jet recording, and then, besides the main ink droplets required for recording, the secondary ink droplets (hereinafter referred to as satellites) or misty ink droplets (hereinafter referred to as mist) is created. The ink droplets that may adhere to the circumference of the ink discharge ports of the recording head are caused by the satellites or mist adhering to it.) The adhesion of such foreign substances may hinder the flight of ink to result in the deviation of impact positions of the ink droplet or to break the ink droplets into splash, or the satellites and mist may clog some of the ink discharge ports, thus causing the defective discharges (or even disabled discharges in some case).
Usually, therefore, an arrangement is made so that the discharge port surface is cleaned periodically or at a specific timing. As to the cleaning of the conventional ink jet recording apparatus, various structures have been disclosed in the specifications of Japanese Patent Laid-Open Application No. 06-340082, Japanese Patent Laid-Open Application No. 07-009674, Japanese Patent Laid-Open Application No. 07-052396, and some others, for example.
FIG. 1 is a view which schematically shows one structural example of a recording head. In FIG. 1, the head 2000 has a plurality of nozzles arranged in lines to form the nozzle array 2030 of one color portion. Then, the head unit 600 is formed by arranging a plurality of heads in parallel. The important portions of the side edge of the head 2000 are sealed by use of silicon sealant 2010 in order to prevent ink from leaking or entering the head from the outside.
Now, for example, if it is intended to wipe the face plane 2020 of the head unit 600 continuously with one wiper (not shown) (hereinafter referred to as a wiper blade or blade) by allowing the carriage having the head unit 600 mounted on it to move in the direction orthogonal to the nozzle arrays, the wiper is in contact with the sealant 2010 when it passes the surface thereof, which creates the stick slipping phenomenon to cause the wiper to vibrate abnormally. As a result, the ink droplets that have been scraped off by the wiper are caused to splash around eventually in some cases. The ink droplets thus splashed at that time adhere to the recording sheet, and may cause the degradation of print quality after all. The splashed ink droplets not only stain the surrounding portions, but also, the circumference of the head that has been wiped off, and adhere to the nozzles and invite the phenomenon described above that may result in the defective printing.
In order to avoid any contact between the wiper and the sealant, it may be possible to use the wiper whose width is smaller than the gap between sealants which are applied in parallel, and then, wiping is performed in the direction parallel to the nozzle arrays. In this case, the stick slipping phenomenon can be avoided, but the probability becomes much higher than the former that the dust particles and solidified ink are in contact with the nozzles. The defective prints may be created more often. Therefore, it is desirable to provide the wiping means executable in the direction orthogonal to the nozzle arrays, while avoiding any contact with the sealants.
Now, if the relative movements of the wiper and the head are too fast, there may take place a phenomenon that ink tends to pass through the wiper, making it difficult to attain the anticipated effect of wiping in some cases. It is preferable to execute wiping rather at slower relative speeds. However, in recent years, along with the development of higher speed printing, the carriage having the head unit mounted on it reciprocates at much higher speeds. If the speeds of such carriage should be made slower to obtain a good wiping effect, it may inevitably takes a longer time to complete the intended wiping operation. There is a fear, then, that the attainment of a higher printing is hindered after all.
Also, when the cleaning operation is repeatedly executed, the wiper is stained by the adhesion of ink or the like. In some cases, such ink or particles that have adhered to the wiper may be transferred to nozzles and others and adhere again to them. There is then proposed a structure whereby to arrange a cleaner to clean the wiper. However, when the blade cleaner that cleans the wiper has come to its saturation, the cleaning performance is lowered (degraded) so that the recording head is wiped with ink droplets remaining on the wiper blade. As a result, a problem is encountered that the defective recording takes place due to the defective discharges caused by the degraded wiping performance.
In order to solve this problem, (1) making the blade cleaners exchangeable, the blade cleaners are replaced before coming to the saturation; (2) with the provision of an ink absorbent whose capacity is large enough to enable the blade cleaner to serve as long as the life of the main body of the apparatus, thus preventing the saturation; and (3) ink absorbed by the blade cleaner is squeezed out to prevent the saturation, among some other preventive means.
However, the method (1) has a drawback that the user finds it extremely inconvenient to make such replacement (that is, the operativity is extremely poor); the method (2) requires a large space, making the apparatus larger unnecessarily; and the method (3) the squeezing mechanism and an additional driving source are needed to make the costs of manufacture higher significantly. Thus, there are still problems yet to be solved in this respect.
Further, as shown in FIGS. 2A and 2B, a wiper blade 10 demonstrates the most effective wiping effect (the effect of wiping off) when its leading end is in contact with the recording head 2000 that moves in the direction indicated by an arrow in FIG. 2A. This has been confirmed by experiments. On the other hand, if the belly portion of the wiper blade 10 is slidably in contact with the discharge port surface of the recording head 2000 as shown in FIG. 2B, it is impossible to obtain the wiping effect sufficiently. Also, in the state where the belly portion of the wiper blade 10 is slidably in contact with the discharge port surface as shown in FIG. 2B, the wiper blade 10 is pressed strongly to the discharge port surface 2020 of the recording head 2000. As a result, the discharge port surface 2020 becomes subjected to damages, and in order to secure the durability of the discharge port surface 2020, it is necessary to enhance the strength of that surface, creating the problem that the costs of manufacture are increased significantly. It is, therefore, very important to set appropriately the amount of approach (the amount of overlapping) of the wiper blade 10 to the recording head 2000 (the discharge port surface thereof) when determining the effectiveness of wiping performance. It is equally important to exercise a highly precise positioning when the wiper blade is arranged for the recording head.
With a view to solving the problems discussed above, the present invention is designed. It is an object of the invention to provide an ink jet printer provided with a wiping unit capable of wiping only the portions that need it, while optimally keeping the free length of the wiper; the amount of overlapping with the recording head; and the slower speeds of relative movements of the head and the wiper when wiping the ink jet recording head which is able to execute recording at high speeds.
It is another object of the invention to provide an ink jet recording apparatus and a cleaning unit by making the absorbing amount of ink smaller for a blade cleaner without making its capacity larger so as to secure the cleaning preformation for a long time with a simpler structure in order to maintain a long-term and stable wiping performance at a higher level when wiping the recording head, hence eliminating the defective recording reliably.
It is still another object of the invention to provide an ink jet recording apparatus capable of securing stably the amount of approach of wiper blades to the recording means in an appropriate value in higher precision, and also, capable of securing the amount of approach of the wiper blades constantly with respect to the switchable height of the carriage to materialize the wiping operation that can reliably remove the ink adhering to the discharge port surface of the recording head, hence eliminating the degradation of image quality due to the defective discharges.
It is another object of the invention to provide an ink jet printer which comprises a wiper member for wiping the surface of the ink jet recording head, and the ink jet recording head and the wiper member move in the same direction each other to wipe the surface of the ink jet recording head by one operation.
It is still another object of the invention to provide an ink jet printer provided with a wiper member for wiping the surface of the ink jet recording head in which the ink jet recording head and the wiper member move in the same direction each other; the moving speed of the wiper member is arranged to be faster than the moving speed of the ink jet recording head for wiping the surface of the ink jet recording head by one operation of the wiper member, and also, a cleaning mechanism is provided for cleaning the wiper member.
It is a further object of the invention to provide an ink jet printer provided with a wiper member for wiping the surface of the ink jet recording head, which comprises at least one recording head having sealant on both sides of the surface surrounding a nozzle array, and being movable in the direction at right angles to the sealant; and at least one rotational wiper member having its leading end to move in the same direction as the recording head for wiping the nozzle array without contacting with the sealant, and then, the nozzle arrays are wiped by one operation of the wiping member.
It is a still further object of the invention to provide an ink jet recording apparatus provided with a wiper blade for wiping the discharge port surface of recording means for recording by discharging ink to a recording medium, which comprises a first blade cleaner and a second blade cleaner for the wiper blade to contact therewith after wiping the discharge port surface.
It is another object of the invention to provide a cleaning unit provided with a wiper blade for wiping the discharge port surface of recording means for recording by discharging ink to a recording medium, which comprises a first blade cleaner and a second blade cleaner for the wiper blade to contact therewith after wiping the discharge port surface.
It is still another object of the invention to provide an ink jet recording apparatus for recording by discharging ink from recording means to a recording medium, and the discharge port surface of recording means thereof being wiped by the rotation of a plurality of wiper blades in the moving direction of the recording means, which comprises rotation means for rotating wiper blades; elevation means for elevating a wiper unit by swinging; a contact member being in contact with the guiding surface of a carriage; and bias means for biasing the contact member to the guiding surface, and then, the swinging center of the wiper unit is arranged to be coaxial with the axial center of one rotation shaft of the rotation means.
Other objectives and advantages besides those discussed above will be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.